A silicon crystal-based solar cell employing a silicon substrate and having a pn junction formed on the silicon substrate is currently on the mainstream. As a solar cell capable of achieving a higher photoelectric conversion efficiency than the silicon crystal-based solar cell, there is a solar cell employing a compound semiconductor of a direct-transition type having a greater optical-absorption coefficient. Many of compound semiconductor solar batteries employing a compound semiconductor currently under development is of a multi-junction structure having a plurality of photoelectric conversion layers with a pn junction and each photoelectric conversion layer having different band gap from one another. Therefore, since a sunlight spectrum can be utilized effectively, a higher photoelectric conversion efficiency than the compound semiconductor solar cell having one photoelectric conversion layer can be obtained. Particularly, a solar cell used for an artificial satellite or the like requires a high photoelectric conversion efficiency and reduction in weight. In light of the above, forming a compound semiconductor solar cell having a multi-junction structure on a resin film is considered.
FIG. 10 represents a solar cell string disclosed in WO99/62125 (PTD 1) formed by electrically connecting solar batteries employing a compound semiconductor. Solar batteries 152, 158 have corresponding integral bypass diodes 154, 160 respectively to form a solar cell string by means of an interconnector.
A first interconnector 164 connects a front contact 155 formed on a cascade cell 156 having a plurality of photoelectric conversion layers in solar cell 152 and a front contact 159 in solar cell 158, so that solar cell 152 and solar cell 158 are electrically connected. Second interconnector 165 connects front contact 155 of solar cell 152 and a back contact 163 of solar cell 158, so that solar cell 152 and solar cell 158 are electrically connected. The numerals 153 and 161 indicate front contacts. The numeral 157 indicates a back contact. The numeral 162 indicates a cascade cell having a plurality of photoelectric conversion layers.